Studies of the projection of single Ia fibers from medial gastrocnemius, lateral gastrocnemius and soleus muscles to motoneurons supplying each of these three muscles in the cat will be continued. The data to be gathered includes the convergence in each system, the average individual EPSP amplitudes and the shapes of the EPSP'S in order to assess the specificity of the projections. Frog spinal reflexes are under study in order to better interpret reflexes obtained previously from supernumerary limbs. These experiments will include intracellular recording from motoneurons. Anatomical investigations will characterize the projections from afferent fibers of the supernumerary limb into the spinal cord.